<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>this</title>
</head>
<body>
<input type="button" value="点我" onclick="fun(this)">

<!--this代表了这个input对象-->

<input type="button" value="点我" onclick="fun(this)">
        <script>
            function fun(obj) {
                     obj.value = 'dog';
                     console.log(obj);
                }
        </script>


</body>
</html>